Some of the known torque limiters for transmitting a torque of a limited value between a first rotatable member and a second rotatable member disposed in a coaxial relationship use a spring. In a typical torque limiter of this type, the first rotatable member is formed with an engagement recess in an inner peripheral part thereof, and the second rotatable member is provided with a roller and a spring for urging the roller into engagement with the engagement recess. The maximum value of the torque (torque limit value) that can be transmitted between the first rotatable member and the second rotatable member is determined by the spring force which the spring applies to the roller. See Patent Documents 1 and 2, for instance.
In another typical torque limiter using a spring, the first rotatable member is formed with an engagement recess in an outer peripheral part thereof, and the second rotatable member is provided with an arm having a free end configured to be selectively engaged by the engagement recess and a spring for urging the arm into engagement with the engagement recess. The maximum value of the torque that can be transmitted between the first rotatable member and the second rotatable member is determined by the spring force which the spring applies to the arm. See Patent Document 3, for instance.